Sublime
An inspiration engine for ideas
Design Club - Super Mario Bros: Level 1-1 - How Super Mario Mastered Level Design
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DOOM was extremely humane software. It let you play with your friends, even in the shareware version. And along with the game itself, id released tools which allowed anyone to easily modify the game’s levels and assets, and then share them for others to use. This created a thriving ecosystem that exists to this day.